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Full text of "Text Book Of Mechanical Engineering"

Appendix VI.

light cut is taken by the wheel, work can be spoilt by over-
grinding, and a very small advance of cutting depth together with
a rapid traverse is the best means of securing accuracy. At the
same time the work should be well watched and continuously
gauged. Lastly, the machines should be constructed so as to
move the work under the wheel in the opposite direction to the
rotation of the latter, and with these preliminaries we will now
examine the grinding machines themselves.

As the work to be ground must have been roughed out
in a lathe, a planer, a slotting machine, a boring machine,
or some other well-known machine tool, it is evident that the
general form of the grinding machine for each purpose must
partake of the character of the particular roughing machine
adopted, and thus we have cylindrical, surfacing, vertical-spindle,
and internal grinders. All the tools to be described are the
manufacture of Mr. J. E. Reinecker, and the drawings have been
kindly supplied by Messrs. Pfeil & Co.

The Cylindrical Grinding Machine, shewn in Fig. 935, is
naturally of lathe form. Upon a bed A is placed a long table B,
for the purpose of carrying the driving headstock c and the poppet
head r>; and the work is rotated between the centres by the
pulley E through the carrier F, the drive being from the first
countershaft K through cone pulleys j H and long drum G. The
slide or table B moves to right or left for a somewhat rapid
traverse, and carries a second table L, to which the headstocks
are bolted. This upper table maybe swivelled through 15 on
either side of the long axis, round a central stud, by means
of the tangent screw j, for the purpose of accommodating tapered
work, but is fixed to the table B by end bolts when grinding is
proceeding. At each end of the traverse stroke the tappets M M
alternately engage the lever N, which puts one or other of the
bevel wheels PP in gear and so reverses the table, the positive
motion of the clutch being secured by the action of the spring
stop k; and the drive is from countershaft K through cones Q R
and thence by bevels p p to a pinion and rack underneath the
table. At each reversal the lever N also strikes a second lever
s, which turns the ratchet wheel x through spur gear, thereby
causing the emery-wheel carriage to be drawn nearer to the work,